Friction weld coaxial connector and interconnection method

ABSTRACT

A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by friction welding is provided with a monolithic connector body with a bore dimensioned for an interference fit with an outer diameter of the outer conductor. A friction groove may be formed around the leading end of the outer conductor by application of a friction weld support against the inner diameter and leading end of the outer conductor. The friction groove may include a material chamber formed between a radial friction protrusion of the bore and a bottom of the friction groove. The friction weld support may be provided with ceramic surfaces contacting the outer conductor, a stop shoulder dimensioned to abut a cable end of the bore and/or an elastic insert seated within an inner conductor bore.

BACKGROUND

1. Field of the Invention

This invention relates to electrical cable connectors. Moreparticularly, the invention relates to a coaxial cable connectorinterconnectable via friction welding.

2. Description of Related Art

Coaxial cable connectors are used, for example, in communication systemsrequiring a high level of precision and reliability.

To create a secure mechanical and optimized electrical interconnectionbetween the cable and the connector, it is desirable to have generallyuniform, circumferential contact between a leading edge of the coaxialcable outer conductor and the connector body. A flared end of the outerconductor may be clamped against an annular wedge surface of theconnector body via a coupling body. Representative of this technology iscommonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz.Although this type of connector is typically removable/re-useable,manufacturing and installation is complicated by the multiple separateinternal elements required, interconnecting threads and relatedenvironmental seals.

Connectors configured for permanent interconnection via solder and/oradhesive interconnection are also well known in the art. Representativeof this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep.8, 1998 to Bufanda et al. However, solder and/or adhesiveinterconnections may be difficult to apply with high levels of qualitycontrol, resulting in interconnections that may be less thansatisfactory, for example when exposed to vibration and/or corrosionover time.

Competition in the coaxial cable connector market has focused attentionon improving electrical performance and long term reliability of thecable to connector interconnection. Further, reduction of overall costs,including materials, training and installation costs, is a significantfactor for commercial success.

Therefore, it is an object of the invention to provide a coaxialconnector and method of interconnection that overcomes deficiencies inthe prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention,where like reference numbers in the drawing figures refer to the samefeature or element and may not be described in detail for every drawingfigure in which they appear and, together with a general description ofthe invention given above, and the detailed description of theembodiments given below, serve to explain the principles of theinvention.

FIG. 1 is a schematic external isometric view of an exemplary embodimentof a coaxial connector installed upon a coaxial cable with a couplingnut spaced away from the connector along the cable forconnector-to-cable interconnection.

FIG. 2 is a schematic isometric view of the coaxial connector of FIG. 1installed upon a coaxial cable, with the coupling nut seated upon thecoaxial connector.

FIG. 3 is a schematic isometric view of the coaxial connector of FIG. 1.

FIG. 4 is a schematic cross section side view of FIG. 2.

FIG. 5 is an enlarged view of area A of FIG. 4.

FIG. 6 is a schematic exploded isometric partial cut-away view of theconnector and cable of FIG. 1.

FIG. 7 is a schematic isometric partial cut-away view of the connectorbody of FIG. 5.

FIG. 8 is a schematic isometric view of an alternative connector bodywith notches on a flange of the connector body.

FIG. 9 is a schematic isometric view of an alternative connector bodywith longitudinal knurls on the connector body outer diameter.

FIG. 10 is a schematic isometric cut-away view of the overbody of FIG.5.

FIG. 11 is an enlarged view of area B of FIG. 4.

FIG. 12 is a schematic cross section side view of an alternativeoverbody with corrugation on an inner diameter of the cable end.

FIG. 13 is a schematic cross section side view of an alternativeoverbody with a stepped surface on an inner diameter of the cable end.

FIG. 14 is a schematic cross section side view of a coaxial connectorembodiment with an inner conductor end cap.

FIG. 15 is a schematic cross section side view of an alternative coaxialconnector embodiment with a minimally extending shoulder.

FIG. 16 is an enlarged view of area B of FIG. 15.

FIG. 17 is a schematic exploded view of an alternative coaxial connectorembodiment with a friction weld support.

FIG. 18 is a schematic isometric partial cut-away view of thealternative coaxial connector of FIG. 17, with the coaxial cablepositioned in the bore, ready for insertion of the friction weldsupport.

FIG. 19 is a schematic isometric partial cut-away view of thealternative coaxial connector of FIG. 17, with the friction weld supportseated within the bore, ready for initiation of friction weld rotation.

FIG. 20 is a schematic side view of FIG. 19.

FIG. 21 is an enlarged view of area A of FIG. 20.

DETAILED DESCRIPTION

Aluminum has been applied as a cost-effective alternative to copper forthe conductors in coaxial cables. However, aluminum oxide surfacecoatings quickly form upon air-exposed aluminum surfaces. These aluminumoxide surface coatings may degrade traditional mechanical, solder and/orconductive adhesive interconnections.

The inventors have recognized that increasing acceptance of coaxialcable with solid outer conductors of aluminum and/or aluminum alloyenables connectors configured for interconnection via friction weldingbetween the outer conductor and a connector body which may also be costeffectively provided, for example, formed from aluminum and/or aluminumalloy.

An exemplary embodiment of a friction weldable coaxial connector 2 isdemonstrated in FIGS. 1-4. As best shown in FIG. 4, a unitary connectorbody 4 is provided with a bore 6 dimensioned to receive the outerconductor 8 of a coaxial cable 9 therein. An inward projecting shoulder10 angled toward a cable end 12 of the connector body 4 forms an annularfriction groove 14 open to the cable end 12. As best shown in FIG. 5,the friction groove 14 is dimensioned to receive a leading edge of theouter conductor 8 therein, a thickness of the outer conductor 8preventing the outer conductor 8 from initially bottoming in thefriction groove 14, forming an annular material chamber 16 between theleading edge of the outer conductor 8 and the bottom of the frictiongroove 14, when the outer conductor 8 is initially seated within thefriction groove 14.

One skilled in the art will appreciate that connector end 18 and cableend 12 are applied herein as identifiers for respective ends of both theconnector and also of discrete elements of the connector describedherein, to identify same and their respective interconnecting surfacesaccording to their alignment along a longitudinal axis of the connectorbetween a connector end 18 and a cable end 12.

The bore sidewall 20 may be diametrically dimensioned to create afriction portion 22 proximate the friction groove 14. The frictionportion 22 creates additional interference between the bore sidewall 20and the outer diameter of the outer conductor 8, to increase frictionduring friction welding.

Prior to interconnection via friction welding, also known as spinwelding, the cable end 12 may be prepared, as best shown in FIG. 6, bycutting the cable 9 so that the inner conductor 24 extends from theouter conductor 8. Also, dielectric material 26 between the innerconductor 24 and outer conductor 8 may be stripped back and a length ofthe outer jacket 28 removed to expose desired lengths of each, includinga sacrificial portion of the outer conductor 8 which is consumed duringthe friction welding process.

To initiate friction welding, the connector body 4 is rotated withrespect to the outer conductor 8 during seating of the leading edge ofthe outer conductor 8 within the friction portion 22 and into thefriction groove 14, under longitudinal pressure. During rotation, forexample at a speed of 3000 to 5000 revolutions per minute, the frictionbetween the leading edge and/or outer diameter of the outer conductor 8and the friction portion 22 and/or friction groove 14 of the bore 6generate sufficient heat to soften the leading edge and/or localizedadjacent portions of the outer conductor 8 and connector body 4, forgingthem together as the sacrificial portion of the outer conductor 8 formsa plastic weld bead that flows into the material chamber 16 to fuse theouter conductor 8 and connector body 4 together.

Projection of the shoulder 10 into the signal space between the outerconductor 8 and the inner conductor 24 (see FIG. 5) may generate animpedance discontinuity that degrades electrical performance. Suchimpedance discontinuities may be minimized by reducing the structure ofthe friction groove 14 to the bore sidewall 20 and a friction groovebottom 52 by applying an inward projecting shoulder 10 with limitedoverhang and/or extent less than an inner diameter of the outerconductor 8, for example as shown in FIGS. 15 and 16. However, this mayrequire that the outer conductor 8 have a significantly increasedthickness, material strength characteristics and/or an outer conductor 8supporting dielectric material 26 with high temperature resistance, toavoid inward deformation and/or collapse of the outer conductor 8 duringfriction welding.

Alternatively, a friction weld support 54 may be applied during thefriction welding, for example as shown in FIGS. 17-21. The friction weldsupport 54 has an insert body 56 with a generally cylindrical insertportion 58 provided at the cable end 12 with an outer diameterdimensioned to seat within and thereby support the inner diameter of theouter conductor 8. The travel of the insert portion 58 within the innerdiameter of the outer conductor 8 may be limited, when the outerconductor 8 is seated within the bore 6, by a stop shoulder 60 at aconnector end 18 of the insert portion 58 that abuts a connector end 18of the bore 6 when the insert portion 58 is fully seated within theinner diameter of the leading end of the outer conductor 8.

As best shown in FIG. 21, inserted within the inner diameter of theouter conductor 8 seated within the bore 6, the friction weld support 54provides an inner sidewall 62 and/or friction groove bottom 52 of anouter conductor leading edge friction groove 14, retaining the outerconductor 8 against the bore sidewall 20 as described herein above.However, after friction welding has been completed, the friction weldsupport 54 may be extracted, leaving a weld between the outer conductor8 and connector body 4, without structure projecting into the signalspace.

To further enhance friction with the bore sidewall 20, the bore 6 may bedimensioned with a progressive interference fit tapered to a minimuminner diameter towards the connector end 18, as best shown in FIG. 21. Afinal inward projecting interference protrusion 64 may be appliedproximate the connector end 18 of the bore 6 to define a materialchamber 16 between the interference protrusion 64 and the frictiongroove bottom 52 to enable molten intermingling of the sacrificialmaterial at the leading edge of the outer conductor and the boresidewall 20 during friction welding.

To minimize friction between the friction weld support 54 and the outerconductor 8, at least the insert portion 58 of the friction weld support54 may be provided as a low friction heat resistant material such asceramic material. Alternatively, the entire friction weld support 54 maybe formed from the selected low friction heat resistant material.Thereby, the friction weld support 54 may have friction and thermaldamage resistance characteristics as well as limited dimensionalvariation during friction welding, enabling repeated use of a singlefriction weld support 54 with multiple interconnections.

To avoid interference with the inner conductor 24, the insert body 56may be provided with an inner conductor bore 66, coaxial with theinsertion portion 58. A diameter of the inner conductor bore 66 isgreater than an outer diameter of an inner conductor. An elastic insert68 may also be provided, seated within the inner conductor bore 66 tomaintain the position of the friction weld support 54 during apparatusassembly for friction welding, as shown for example in FIG. 20.

An extraction shoulder 70 may be provided proximate a connector end 18of the insert body 56 for ease of insertion/extraction before and afterfriction welding.

Friction welding utilizing the friction weld support 54 may applyadditional steps to the procedure described herein above. For example,the dielectric material 26 may be stripped back from the leading end ofthe outer conductor 8, within the cable 9, to provide space for theinsertion of the friction weld support 54 such that, when the leadingedge of the outer conductor 8 is seated within the friction groove 14,the friction weld support 54 does not contact the dielectric material26.

During the friction weld step, the friction weld support 54 may bealternatively rotationally locked with either the connector body 4 orthe cable 9. Further, the longitudinal force applied during the frictionwelding may be applied via the friction weld support 54, as the stopshoulder 60 will abut the connector body 4 at a connector end 18 of thebore 6, driving the connector body 4 ahead of it towards the leading endof the outer conductor 8.

The ready for rotation assembly wherein the leading edge of the outerconductor 8 is seated within the friction groove 14, formed by thecombination of the connector body 4 and the friction weld support 54,may be assembled for the friction welding in an order best suited to thecharacteristics of the outer conductor 8 utilized. For example, wherethe outer conductor 8 is fragile, the outer conductor 8 may be insertedwithin the bore 6 prior to seating of the friction weld support 54within the bore 6 and against the inner diameter of the outer conductor8, for example as shown in FIG. 18. Then, the friction weld support 54may be inserted within the bore 6 and inner diameter of the outerconductor 8, the bore 6 supporting the outer conductor 8 from collapseas the friction weld support 54 is inserted, for example as shown inFIG. 19. Alternatively, the friction weld support 54 may be insertedwithin the bore 6 before the leading edge of the outer conductor 8 isinserted directly into the combined friction groove 14 formed thereby.

Because the localized abrasion of the friction welding process can breakup any aluminum oxide surface coatings in the immediate weld area, noadditional care may be required with respect to removing or otherwisemanaging the presence of aluminum oxide on the interconnection surfaces.

An overbody 30, as shown for example in FIG. 10, may be applied to theconnector body 4 as an overmolding of polymeric material. The overbody30 increases cable to connector torsion and pull resistance. Theoverbody 30 may also provide connection interface structure at theconnector end 18 and further reinforcing support at the cable end 12,enabling significant reductions in the size of the connector body 4,thereby reducing overall material costs.

Depending upon the applied connection interface 31, demonstrated in theexemplary embodiments herein as a standard 7/16 DIN interface, theoverbody 30 may be provided with an overbody flange 32 and longitudinalsupport ridges 34 for a coupling nut 36. The coupling nut 36 is retainedupon the support ridges 34 at the connector end 18 by an overbody flange32 and at the cable end 12 by a retention spur 38 provided on at leastone of the support ridges 34. The retention spur 38 may be angled towardthe connector end 18, allowing the coupling nut 36 to be placed over thecable 9 initially spaced away from the coaxial connector 2 duringinterconnection (see FIG. 1), but then allowing the coupling nut 36 tobe passed over the retention spur 38 and onto the support ridges 34 fromthe cable end 12, to be thereafter retained upon the support ridges 34by the retention spur(s) 38 (see FIG. 2) in close proximity to theconnector interface 31 for connector to connector mating. The supportridges 34 reduce polymeric material requirements of the overbody 30while providing lateral strength to the connector/interconnection 2 aswell as alignment and retention of the coupling nut 36.

The overbody 30 may also extend from the connector end 18 of theconnector body 4 to provide portions of the selected connector interface31, such as an alignment cylinder 39 of the 7/16 DIN interface, furtherreducing metal material requirements of the connector body 4.

The overbody flange 32 may be securely keyed to a connector body flange40 of the connector body 4 and thereby with the connector body 4 via oneor more interlock apertures 42 such as holes, longitudinal knurls 43,grooves, notches 45 or the like provided in the connector body flange 40and/or outer diameter of the connector body 4, as demonstrated in FIGS.7-9. Thereby, as the polymeric material of the overbody 30 flows intothe interlock apertures 42 during overmolding, upon curing the overbody30, for example as shown in FIG. 10, is permanently coupled to androtationally interlocked with the connector body 4.

As best shown in FIG. 11, the cable end 12 of the overbody 30 may bedimensioned with an inner diameter friction surface 44 proximate that ofthe coaxial cable outer jacket 28, enabling polymeric friction weldingbetween the overbody 30 and the outer jacket 28, as the connector body 4and outer conductor, thereby eliminating the need for environmentalseals at the cable end 12 of the connector/cable interconnection. Duringfriction welding, the coaxial connector 2 is rotated with respect to thecable 9. Friction between the friction surface 44 and the outer diameterof the outer jacket 28 heats the respective surfaces to a point wherethey begin to soften and intermingle, sealing them against one another.To provide enhanced friction and allow voids for excess flow due tofriction displacement and add key locking for additional strength, theouter jacket 28 and and/or the inner diameter of the overbody 30 may beprovided as a series of spaced apart annular peaks of a contour patternsuch as a corrugation 46, as shown for example in FIG. 12, or a steppedsurface 48, as shown for example in FIG. 13. Alternatively, the overbody30 may be sealed against the outer jacket 28 with an adhesive/sealant ormay be overmolded upon the connector body 4 after interconnection withthe outer conductor 8, the heat of the injected polymeric materialbonding the overbody 30 with and/or sealing against the outer jacket 28.

The inner conductor 24 extending from the prepared end of the coaxialcable 9 may be selected to pass through to the connector end 18 as aportion of the selected connection interface 31, for example as shown inFIG. 4. If the selected coaxial cable 9 has an inner conductor 24 thathas a larger diameter than the inner conductor portion of the selectedconnector interface 31, the inner conductor 24 may be ground at theconnector end 18 to the required diameter.

Although a direct pass through inner conductor 24 advantageouslyeliminates interconnections, for example with the spring basket of atraditional coaxial connector inner contact, such structure mayintroduce electrical performance degradation such as PIM. Where theinner conductor 24 is also aluminum material some applications mayrequire a non-aluminum material connection point at the innercontact/inner conductor of the connection interface 31. As shown forexample in FIG. 14, a center cap 50, for example formed from a metalsuch as brass or other desired metal, may be applied to the end of theinner conductor 24, also by laser or friction welding. To apply thecenter cap 50, the end of the inner conductor 24 is ground to provide apin corresponding to the selected socket geometry of the center cap 50.To allow material inter-flow during welding attachment, the socketgeometry of the center cap 50 and or the end of the inner conductor 24may be formed to provide material gaps as described with respect to thematerial chamber 16 described herein above.

One skilled in the art will appreciate that the connector andinterconnection method disclosed has significant material costefficiencies and provides a permanently sealed interconnection withreduced size and/or weight requirements.

Table of Parts 2 coaxial connector 4 connector body 6 bore 8 outerconductor 9 cable 10 shoulder 12 cable end 14 friction groove 16material chamber 18 connector end 20 bore sidewall 22 friction portion24 inner conductor 26 dielectric material 28 outer jacket 30 overbody 31connection interface 32 overbody flange 34 support ridge 36 coupling nut38 retention spur 39 alignment cylinder 40 connector body flange 42interlock aperture 43 longitudinal knurl 44 friction surface 45 notch 46corrugation 48 stepped surface 50 center cap 52 friction groove bottom54 friction weld support 56 insert body 58 insert portion 60 stopshoulder 62 inner sidewall 64 interference protrusion 66 inner conductorbore 68 elastic insert 70 extraction shoulder

Where in the foregoing description reference has been made to materials,ratios, integers or components having known equivalents then suchequivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin considerable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, representativeapparatus, methods, and illustrative examples shown and described.Accordingly, departures may be made from such details without departurefrom the spirit or scope of applicant's general inventive concept.Further, it is to be appreciated that improvements and/or modificationsmay be made thereto without departing from the scope or spirit of thepresent invention as defined by the following claims.

We claim:
 1. A method for interconnecting a coaxial connector with asolid outer conductor coaxial cable, comprising the steps of: providinga monolithic connector body with a bore; a sidewall of the boreproximate a connector end dimensioned for an interference fit with anouter diameter of the outer conductor; inserting a leading end of thecoaxial cable into the bore, until a leading end of the outer conductorseats in an interference fit within the bore; inserting a friction weldsupport within an inner diameter of the leading end of the outerconductor; the friction weld support cooperating with the bore to forman annular friction groove open to a cable end, around the leading endof the outer conductor; and rotating the connector body about alongitudinal axis of the leading end of the coaxial cable, whileapplying a longitudinal force driving the friction groove against theleading end of the outer conductor.
 2. The method of claim 1, whereinthe outer conductor and the connector body are each one of aluminum andaluminum alloy material.
 3. The method of claim 1, wherein the frictiongroove is provided with an annular material chamber at a connector endof the friction groove.
 4. The method of claim 3, wherein the annularmaterial chamber is a portion of the friction groove between a radialinward friction protrusion of the bore and the connector end of thefriction groove.
 5. The method of claim 1, wherein the rotation andlongitudinal force are applied until heat sufficient to melt the leadingend of the outer conductor is generated.
 6. The method of claim 1,wherein the rotation and longitudinal force generate a friction weldbetween the outer conductor and the connector body.
 7. The method ofclaim 1, wherein the friction weld support is rotationally locked withthe coaxial cable during the rotation.
 8. The method of claim 1, whereinthe friction weld support is rotationally locked with the connector bodyduring the rotation.
 9. The method of claim 1, wherein the longitudinalforce is applied by the friction weld support.
 10. The method of claim1, wherein an outer diameter of a cable end of the friction weld supportis ceramic material.
 11. The method of claim 1, wherein the frictionweld support is provided with a radial outward stop shoulder; the stopshoulder abutting the connector body at a connector end of the bore. 12.The method of claim 1, further including the step of overmolding theconnector body attached to the end of the coaxial cable with a polymericoverbody.
 13. The method of claim 1, further including the steps ofpreparing the leading end of the cable end prior to insertion into thebore by removing a portion of the outer conductor so that an innerconductor extends therefrom, removing a portion of a dielectric materialbetween the inner conductor and the outer conductor such that when theleading edge of the outer conductor is seated within the frictiongroove, the friction weld support does not contact the dielectricmaterial; and stripping back a portion of a jacket from the outerconductor.
 14. The method of claim 1, further including providing anoverbody of polymeric material upon an outer diameter of the connectorbody, the overbody extending from the cable end of the connector body,an inner diameter of the overbody extending from the cable end of theconnector body provided as a friction surface dimensioned for aninterference fit upon an outer diameter of a jacket of the coaxialcable.
 15. The method of claim 14, wherein the rotation and longitudinalforce form a friction weld between the outer conductor and the connectorbody and between the overbody and the jacket of the coaxial cable.